During operation of a gas turbine, a blade ring thermally expands due to the high temperature combustion gas flowing thereinside, and clearance between the blade ring and the tips of blades is easily increased. However, the increase of clearance is undesirable in terms of stably maintaining the performance of the gas turbine.
Therefore, a channel through which cooling steam (cooling medium) is flowed is provided in the blade ring, and thermal expansion of the blade ring is suppressed (for example, refer to Patent Documents 1 and 2 below). In the gas turbine, a plurality of combustors are arranged in the circumferential direction in the upstream side in the turbine shaft direction of the blade ring. The combustors are also cooled using the cooling steam passing through the blade ring.
In a gas turbine disclosed in Patent Document 1 below, an inner channel and an outer channel are provided as the channel of the cooling steam of the blade ring. The inner channel is formed in the blade ring. The outer channel is connected to the inner channel, is disposed in the outer portion of the blade ring, and is formed in a tubular shape which extends in the circumferential direction of the blade ring.
Moreover, the cooling steam performs heat exchange by being flowed through the inner channel and cools the blade ring, and is fed to the combustor and cools the combustor. The cooling steam (superheated steam) which has reached high temperature due to the heat exchange with the inner channel and the combustor is mainly recovered through the outer channel so as not to increase the temperature of the blade ring.